Control apparatus



Dec. 14, 1965 R. F. RASMUSSEN 3,222,993

CONTROL APPARATUS Filed March 20, 1964 I VALVE 1 DAMPER OPERAT I SIGNALS ING I NETWORK I K 66J 3 SERVO- R I l VALVE I k I DAMPER :12? as SIGNALS l g I 1 VALVE OPERATING l l fii J NETWORK e| L rif l 3 SERVO- r P PULL (5| L VALVE z PULL SOL s '03 SOL \.4| l "$50 j.i, R p 4O INVENTOR. ROBERT E RASMUSSEN ATTORNEY United States Patent 3,222,993 CONTRGL APPARATUS Robert F. Rasmussen, Brooklyn Center, Minm, assignor to Honeywell Inc., a corporation of Delaware Filed Mar. 20, 1964, Ser. No. 353,467 14 Claims. (Cl. 91-20) This invention pertains to control apparatus for dir'igible aircraft, and particularly, this apparatus preferably is concerned with the control of the aircraft about its Z or normally vertical axis. The invention may be embodied in a control apparatus of the dynamic damper type, and thus may be considered a yaw damper.

In many instances such yaw damper utilizes a differential or series arranged servomotor. When the servomotor is used in the series or differential arrangement, it is desired, when the servomotor is not operating, to center the servomotor so that there is a correspondence between the position of the control stick or manually operated rudder pedals of the aircraft and the position of the control surface such as the rudder surface of the craft. The invention herein is in providing an improved centering arrangement for a differential or series servomotor in a dynamic damper. In order to enhance the reliability of the servomotor, a dual redundant or tandem ram fluid type servomotor having two sections has been selected as the operating means for the rudder surface and an improved centering arrangement has been provided herein for such servomotor.

Tandem ram, fluid type servomotors, which thus have a dual redundant feature are old in the prior application of Borgeson and Rasmussen, Serial No. 79,950, filed December 30, 1960, now Patent 3,143,042. Such prior servomotor has an averaging arrangement utilizing a comparator responsive to the operation condition of the tandem servomotors and to the differential fluid pressure across the respective rams of the two servomotor sections.

In addition, such prior art servomotor is provided with a ride along type mechanical type or spring centering arrangement, for the servomotor see FIGURE 2A which discloses the spring centering means 16, which is considered in regard to applicants invent-ion.

An object of this invention is to provide an improved centering means for the tandem rams of a dual redundant servomotor.

A further object of this invention is to provide a separate source of fluid pressure for operating the two sect-ions of a tandem ram type servomotor, and for utilizing the pressure from at least one fluid supply for centering the tandem rams when operation of the servomotor is terminated accidentally or is no longer required.

A further object of this invention is to provide in a dual redundant or tandem ram fluid type servomotor a comparator to obtain an average position of the tandem servomotors which comparator is rendered ineffective upon isolating one tandem ram from its fluid pressure Source.

A further object of this invention is to provide a dual redundant or tandem ram fluid type servomotor with a separate source of pressure fluid operating with its respective power section of the servomotor with fluid pressure operating means for centering the tandem rams upon disengagement of control of said rams from their respective control valves.

It is a further object of this invention to provide in a dual redundant or tandem ram type fluid servomotor each with a separate engage means for conditioning each section for operation, and utilizing a comparator for averaging the displacement of said tandem rams in accordance with the average of their control signals to cause the averaging arrangement to be rendered ineffective when one of the engaged means is moved to its unoperative position, and further wherein fluid pressure means for centering the tandem rams is provided when both engaged means are simultaneously moved to the unoperated position.

The above and other aspects of the invention will be more thoroughly understood in the light of the following detailed description of a presently preferred form of the control apparatus, taken in conjunction with the accompanying drawing in which:

The sole figure is a schematic illustration of the dual redundant servomotor having the improved centering means.

In some types of aircraft which attain in flight substantially high air speed thereby causing large aerodynamic forces on the control surfaces of the aircraft, power means such as servomotors are required to move or activate the surfaces against the action of such large action forces. Where fluid type servomotors are used as surface actuators, a plurality of servomotors arranged in tandem, for example, might be utilized to obtain both suflicient force for operation of the surface, and 'also to derive redundant advantages of a plurality of servomotors. With the servos in tandem, the unit is a compound servomotor.

When such compound servomotor is used in a dynamic damper as a series or differential type servomotor, it is desirable to center such servomotor when it is no longer to be used, thereby to provide a given relationship between a second operator for such control surface, and the control surface position. The centering arrangement for the differential servomotor is effected herein by the application of fluid pressure which has an advantage such as shorter operating time over mechanical centering arrangements as used heretofore in the prior art.

Referring to the figure, an output member 10 is positioned by a compounded servomotor 11. Servomotor 11 is of the dual redundant or tandem ram type comprising a power section 12 having ram 13 and a power section 14 having ram 15. Rams 13 and 15 are interconnected by a piston rod 16.

Associated with power section 12 is an on-off engage valve 20 for preconditioning power section 12 for operation which preferably comprises a first part or upper part 21 in the figure, and an abutting lower part 23. The part 21 includes a multi-land movable spool 22 biased to lower or unoperated position by suitable spring 25. Part 23 includes a multi-land movable spool 24.

Associated with power section 14 is an engage valve 30 for preconditioning power section 14 for operation consisting of an upper section 31 and a lower section 33. The upper section 31 includes a multi-land spool 32 biased to unoperated or downward position in the figure by a suitable spring 35. The lower portion 33 includes a mult-i-land movable spool 34 which abuts spool 32 of upper section 31.

The movable spools 22, 24 of engaged valve 20 are moved about .010 inch from an unoperated to the upper or operated position as shown in the figure, through application of a fluid pressure from source P supplied through a three way pilot valve 40 operated by a pull solenoid 41. Similarly, the movable spools 32, 34 of engage valve 30 are moved about .060 inch from an unoperated to the upper or operated position shown by application of pressure from a fluid pressure source P upon operation of a three way pilot valve 50 controlled from a pull solenoid 51.

Power section 12 is controlled through the operated engage valve 20 from a variably positionable servo control valve 60. The valve is controlled by a valve operating network 61 and thus Valve 60 may be considered an electro-hydraulic valve. The network 61, in addition to receiving signals as from a yaw damper, also receives a follow up signal from a servo operated feedback transducer 62. Similarly, a servo control valve 65 for power section 14 is variably positioned from a valve operating network 66. Network 66 receives damper signals and a feedback signal from transducer 67.

The transducers 62, 67 are operatively related to a comparator 70 and servo operated means. Each transducer consists of two relatively movable parts. One part of transducer 62 is operated by a drive mechanism consisting of a member 68 fast on piston rod 16 which actuates a cam member 69 hearing against the follower 70 of one part of transducer 62.

Similarly, transducer 67 consists of two relatively movable parts, one of which is actuated from the servo operated cam member 69 through a cam follower 71. The other two movable parts of transducer 62, 67 are positioned in accordance with the difference in two pairs of pressures. One pair of pressures is applied to a piston 73 in a comparator section 75, and a second pair of pressures is applied to opposite sides of a piston 74 in a comparator section 76. The function of the comparator is to ultimately effect a resultant positioning of the rams 13, 15 in accordance with the average of both signals from transducers 62, 67.

Pistons 73, 74 are mounted on a rod 78 which is associated with a comparator centering spring arrangement 79 which includes a centering spring 80. Pressure may be applied to the centering arrangement 79 to relieve the rod 78 of the force on spring 80, thereby permitting its displacement in accordance with the differential pressure on the opposed sides of pistons 73, 74. Centering means such as 79 above, correspond in general to the centering means 360 of my prior Patent 3,034,483.

Coming now to the centering control for the power rams 13, 15, the member 68, movable with the piston rod 16, operates a valve rod 86 which positions a spool or plug 87 of a centering valve 88, and also positions a spool 89 of a centering valve 90. The centering valves provide a constant flow rate for large displacements of rod 16 since they are fully opened for moderate displacements, lesser flow rates occur when the centering valve ports are nearly closed by return to center of rod 16. Whenever the power rams 13, 15 depart from a normal position, a similar movement is given to the spools or plugs 87, 89. It will be noted that a first pressure from a source P is supplied to valve 90 and a second but normally equal pressure from a second source P is supplied to valve 88. The pressure ports are of such size as to be open for small displacements of plugs 87, 89.

Operation The operation of this differential fluid type servomotor may now be considered. We assume that the comparator centering arrangement 79 has been operated to unload the rod 78 from the centering spring 80. We also assume that pilot valve 50 has been operated thereby to supply pressure from source P to engage valve 30 moving it to the operated or upper position, shown in the figure, and also there is a supply pressure to servo valve 65. Also, the pilot valve 40 has been operated to supply pressure from a source P to engage valve 20 to effect its operation and displacement to the upper position shown in the figure, and also there is a supply of fluid pressure to servo valve 60.

We may assume that electrical signals similar both in magnitude and polarity are applied to both networks 61, 66 to operate the respective electrohydraulic servo valves 60, 65. Viewing the operation of ram 13 the resulting displacement of servo valve 60 enables fluid from pressure source P to be applied through conduit 97, branch conduit 98, engage valve spool 24, conduit 99, to the left side of servo ram 13. The opposite side of ram 13 is connected through conduit 100, spool 24, conduit 101,

conduit 102, and return side of servo valve 60 to fluid return line 103.

Also comparator pressure is supplied from conduit 97, the operated engage valve spool 24, conduit 108, operated spool 34 of engage valve 30, conduit 109, to the right side of ram 74 in comparator section 76. The opposite side of comparator ram 74 is connected through conduit 110, spool 34, conduit 111, spool 24 of engage valve 20, through conduit 102, valve 60, to return conduit 103.

The pressure on the left side of ram 13 causes the ram 13 to move rightwardly and communicates this motion to the output member 10 that results in the operation of a control surface of an aircraft. The operation of ram 13 is accompanied by the movement of the member 68 and the displacement of spool 89 of the centering valve 90.

In the event that while spool 89 in centering valve 90 upper right, is displaced to the right of its normal position and is fully open for moderate ram displacements, and if the two operated engage valves 20, 30 are both simultaneously in unoperated positions as by closing pilot valves 40, 50 to remove pressure thereon, pressure from the source P upper right, passes through the spool 89 of centering valve 90, conduit 112, spool 22 of unoperated engage valve 20, conduit 113, spool 32 of unoperated engage valve 30, conduit 114, to the right side of piston 15 in section 14. With the resulting pressure on the right side of piston 15 the rams 13, 15 are moved leftwardly at a predetermined rate irrespective of their positions due to the full valve opening until near center and moved more slowly thereafter as the valve opening decreases until the spool valve 89 is centered, shutting off" the supply from source P through centering valve 90.

It will also readily appear that correspondingly due to the operation of servo control valve 65, from the same signal as applied to servo control valve 60, when the engage valves are in operated position fluid pressure from the source P is supplied tthrough valve 65, conduit 120, subconduit 121, plug 32 of operated engage valve 30, whereby fluid is transmitted thence to conduit 123, to the left side of piston 15, whereby piston 15 tends to move rightwardly simultaneously with piston 13 for parallel operation. The opposite side of ram 15 is connected through conduit 124, spool 32 of operated engage valve 30, subconduit 125, conduit 126, servo valve 65 to return line 127.

It will also readily appear that pressure in conduit is supplied through spool 32 of engage valve 30, conduit 129, spool 22 of operated engage valve 20, conduit 130, to the left side of ram 73 in comparator section 75. The opposite side of ram 73 is connected through conduit 131, spool 22 of engage valve 20, conduit 132, spool 32 of engage valve 30, conduit 126, servo valve 65 to return line 127.

If the differential pressure in the pair of conduits 120, 126 which are connected to the opposed sides of ram 73, is different from the differential pressure in the pair of conduits 97, 102 connected to the opposed sides of ram 74, a resulting motion is given the rod 78 and thus a resultant motion is given to one part of each of the transducers 62, 67, which motion causes an opposite effect in the respec tive networks 61, 66 resulting in modification in the positions of rams 13 and 15, resulting finally in the rams assuming a position which is the average of the signals from transducers 62, 67.

It will now be seen that if the operated engage valve 20 which serves to transmit fluid from operated servo valve 60 to power ram 13 is moved to the downward or unoperated position from the position shown in the figure, that the spool 22 of engage valve 20 cuts off or isolates the opposed sides of ram 73 of comparator section 75 from conduits 129, 132 and also that spool 24 isolates or cuts off conduits 109, 110 from extending from the opposed sides of comparator ram 74 from conduits 108, 111 and respectively connects conduits 130, 131 and conduits 109, 110 with the returns R R;, for conduits 131, and re turns R R for conduits 109, Hit, 50 that the pressure on opposing sides of comparator rams 73, 74 are the same and the only signals from transducers 62, 67 are due to the displacement of power rams 13, 15.

It will also be apparent that with the engage valve 20 in the unoperated position, that the opposed sides of piston 13 are connected through their conduits 99, 100, respectively through spool 24, conduit 140, operated spool 34, to return R and spool 24, conduit 141, operated spool 34 to return R Thus, the opposed sides of piston 13 are vented to the return.

It will further be apparent that with both engage valves 20, 3%) in the downward or unoperated position from that shown in the figure, that fluid transmission from the servo valves 60, 65 to the respective rams 13, 15 is cut off by spools 24, 34-. Centering of the rams or moving them to a normal position is obtained as follows. Assuming the pistons 13, 15 to the right of their respective positions with a consequent displacement of the spools 87, 39 of valves 88, 95 to the right of their normal positions, fluid from pressure source P upper right, of the figure, passes through the spool valve 89, conduit 112, spool 22 of engage valve 20, conduit 113, spool 32 of engage valve 30, conduit 114, to the right side of piston 115 applying pressure to and moving the pistons 13, 15 at a predetermined rate in accordance with P moving valve plugs 89, 87 toward the left to normal centered positions.

Similarly pressure from supply P upper left, passes through valve 88, conduit 145, spool 34, conduit 141, spool 24, conduit 109, to the right side of piston 13 applying pressure thereto and moving the piston 13 and piston 15 toward the left and to their normal positions. With the movements of pistons 13, 15 and the accompanying movements of spools 87, 89, these spools are moved to their normal positions cutting off the supply pressures P P to conduits 112, 145 to complete the pressurized fluid centering of the servomotor 11.

It will now be apparent that I have provided a novel dual redundant, fluid centered type servomotor having an interlock between a comparator and the engage valves for the two servo power sections wherein movement of one engage valve to unoperated position, as by loss of a single pressure or electrical failure will render the comparator ineffective, and that subsequent control is achieved by one of said servomotor sections. Further that a novel fluid powered centering arrangement has been provided for both sections of the redundant servomotor, so that when both engage valves are moved to their unoperated positions as by electrical faliure to its electro-hydraulic valves, the pistons in the redundant servomotors are moved to a normal unoperated position, which normal position is a desired condition for a series or differential type servomotor used in a damper configuration for controlling an aircraft. While the arrangement has been described for use in a yaw damper, it may be readily applied to dampers in other axes of a craft and for generally similar purposes.

What I claim is:

I. In a dual tandem ram, fluid type compound servomotor having two power sections, a variably positioned first servo valve for one section, a variably positioned second servo valve for the other section, means including an on-off engage valve and first servo valve for transmitting pressure fluid from one fluid pressure source to one power section; means including a second on-off engage valve and second servo valve for supplying fluid pressure from a second pressure source to the other power section; and servo operated, ser-vo centering control valves operable with said rams in said power sections and effective on the two engage valves being in unoperated positions, applying pressure to at least one of said rams to effect return thereof to a normal or centered position.

2. A fluid type compound servometor having a pair of power sections operable in parallel from a centered position to jointly position an output member; a first servo control valve for one section; a second servo control valve for the other section; a first operable engage valve for a first section; a second operable engage valve for a second power section; means for variably positioning both servo valves; means including both servo control and engage valves transmitting fluid to cause operation of both sections; and an additional servo control centering valve positioned by the power sections and effective on termination of such transmission of fluid by both engage valves, transmitting pressure fluid to a power section to effect return of the power sections to said central position.

3. The apparatus of claim 2, and a comparator responsive to differential pressure across both servo valves and to the operation of said power sections; and feedback transducers for controlling both servo valves and operated by said comparator, whereby to obtain an average displacement of the output member in accordance with the average positioning of said servo valves.

4. In a fluid operated, ram type servomotor, a variably displaceable fluid conducting first servo control valve; an engage valve coacting in one position thereof with the servo control valve for transmitting fluid from a pressure source to said servomotor whereby on displacement of the servo control valve fluid pressure is applied to one side of the ram; a second servo control valve positioned by said ram; and means connected with the second control valve and engage valve and effective in another position thereof, causing termination of said transmission of fluid by said engage valve despite displacement of the first servo control valve, and operation of said ram, applying pressure through the second servo control valve and engage valve to the opposite side of the ram to effect centering thereof.

5. In a fluid operated, ram type servomotor, a variably displaceable, electrically operable servo control valve; an engage valve having a first and a second position; means including both valves for transmitting fluid from a pressure source to said servomotor in the first position of the engage valve whereby on displacement of the control valve fluid pressure is applied to one side of the ram; follow up electrical signal means operated by the ram to limit the displacement thereof; a servo centering control valve positioned by said ram; and further means connected with said engage valve and servo centering control valve and effective in the second position of the engage valve, which causes termination of said transmitting of fluid through said operated servo control valve, and operation of said ram from a normal position, applying pressure through the second servo centering control valve to the opposite side of the ram to effect centering thereof.

6. In a fluid operated, ram type servomotor, a variably displaceable servo control valve; an engage valve coating with the control valve for transmitting fluid upon operation of said servo control valve from a pressure source to said servomotor whereby fluid pressure is applied to one side of the ram; a second servo normal position control valve moved to full open position by said ram on small displacements thereof; a further valve displaceable from a normal position; and means including the second control valve effective on termination of transmission of fluid by said engage valve and return of said further valve to its normal position during displacement of said ram, applying pressure through the unoperated engage valve and the returned further valve to the opposite side of said piston to effect centering thereof.

7. In a fluid type servomotor having a pair of tandem power sections operable in parallel from a normal position to jointly position an output member; a first servo control valve for one section; a second servo control valve for the other section; a first engage valve effective when operated for transmitting fluid from a first pressure source on operation of a first control valve to the first servo section; a second engage valve effective on op eration of the second servo control valve for transmitting fluid from a second pressure source to the second servo section; means for similarly variably positioning both servo valves; and additional servo normal position control valves positioned by the power sections and moved to full open condition for even moderate displacement of said sections; and means including said additional servo control valves effective on simultaneous termination of transmission of fluid by both engage valves, transmitting pressure to a power section to ettect return of the power sections to normal position at a predetermined rate irrespective of the extent of operation of the power sections.

8. In a fluid type servomotor having a pair of tandem power sections operable in parallel from a normal position ,to jointly position an output member, comprising: a first servo control valve for one power section; a second servo control valve for the other power section; a first operable two position engage valve for transmitting fluid from a pressure source on operation of the first control valve to the first servo section; a second operable two position engage valve for transmitting fluid from a pressure source to the second servo section; means for variably positioning both servo valves in either direction from a normal position; an additional servo controlled valve having its position controlled by the power section; and means re sponsive both to the displacement of said additional servo control valve, and return of both engage valves to unoperated positions transmitting fluid pressure to a power section to effect return of both power sections to normal position.

9. In a fluid type compound servomotor having a pair of tandem power sections operable in parallel from a normal position to jointly position an output member, comprising: a first servo control valve for one section; a second servo control valve for the other section; a first means for transmitting fluid from a first pressure source on operation of the first controlvalve to the first servo section; a second means for transmitting fluid from a second pressure source to the second servo section on operation of the second control valve; means for similarly variably positioning both servo valves; two additional servo normal position control valves positioned in accordance with the displacement of the power sections; and centering means effective through at least one of said additional servo control valves upon termination of the transmission of fluid through both said means, transmitting fluid pressure from the first pressure source to the first servo section for centering the sections.

10. The apparatus of claim 9, a comparator responsive to the operating conditions of both servo sections; and means responsive to the termination of transmission of fluid by but one transmission means rendering the comparator 'nonresponsive to the operating conditions of both servo sections.

11. The apparatus of claim 9 and means for transmitting fluid pressure through the other one of said additional servo control valves from the second pressure source to said second servo section.

12. In a fluid type servomotor having a pair of power sections operable from a normal position to jointly position an output member, the combination comprising: a

first servo control valve for one section; a second servo control valve for the other section; a first means for transmitting fluid from a first pressure source on operation of the first servo control valve to the first servo section; a second means for transmitting fluid from a second pressure source to the second servo section on operation of the second servo control valve; means for similarly positioning said servo valves; and two additional servo centering control valves positioned in accordance with the displace ment of the power sections; and means effective on termination of transmission of fluid by both fluid transmitting means, transmitting pressure from the first pressure source through one additional servo control valve to the first section and transmitting pressure from the second pressure source through the second additional servo control valve to the second servo section whereby both servo sections are centered.

13. In a fluid type servomotor having a pair of tandem ram power sections operable from a normal position to jointly position an output member: a first operable engage valve responsive to pressure from one source and thereby operable to an operated or engaged position; a second operable engage valve responsive to pressure from a second pressure source and thereby operated to an engaged or operated position; servo control valve means effective upon displacement thereof and during the positioning of both engage valves in the engaged position, effecting operation of both power sections; a servo control valve positioned in accordance with the displacement of said sections; and means effective upon both return of said engage valves to unoperated position and to said second control valve when displaced supplying fluid pressure to one of said sections causing return of both sections to normal position at a predetermined rate irrespective of extent of operation of the rams of the power sections.

14. In a fluid type servomotor having a pair of power sections both operable from a normal position to jointly position an output member; a first servo control valve for one section; a second servo control valve for the other section; a first operable engage valve for transmitting fluid from a first pressure source on operation of the first servo control valve to the first servo section; a second operable engage valve for transmitting fluid from a second pressure source to the second servo section on operation or" the second servo control valve; an additional servo control valve positioned by the power sections; and means responsive both to the additional servo control valve and both engage valves applying centering pressure to one power section to eifect centering operation of said additional servo control valve.

References Cited by the Examiner UNITED STATES PATENTS 2,766,731 10/1956 Brandes 9120 2,995,014 8/1961 Horky 91414 3,081,968 3/1963 Pesola 91-363 SAMUEL LEVINE, Primary Examiner.

FRED E. ENGELTHALER, Examiner. 

1. IN A DUAL TANDEM RAM, FLUID TYPE COMPOUND SERVOMOTOR HAVING TWO POWER SECTIONS, A VARIABLY POSITIONED FIRST SERVO VALVE FOR ONE SECTION, A VARIABLY POSITIONED SECOND SERVO VALVE FOR THE OTHER SECTION, MEANS INCLUDING AN ON-OFF ENGAGE VALVE AND FIRST SERVO VALVE FOR TRANSMITTING PRSSURE FLUID FROM ONE FLUID PRESSURE SOURCE TO ONE POWER SECTION; MEANS INCLUDING A SECOND ON-OFF ENGAGE VALVE AND SECOND SERVO VALVE FOR SUPPLYING FLUID PRESSURE FROM A SECOND PRESSURE SOURCE TO THE OTHER POWER SECTION; AND SERVO OPERATED, SERVO CENTERING CONTROL VALVES OPERABLE WITH SAID RAMS IN SAID POWER SECTIONS EFFECTIVE ON THE TWO ENGAGE VALVES BEING IN UNOPERATED POSITIONS, APPLYING PRES- 